Ni-Pt nanoparticle decorated, C, N-doped titania microparticles with low band gap energy as an efficient catalyst for hydrogen generation from hydrous hydrazine

Abstract

The recent studies demonstrated superior catalytic activity and higher selectivity of carbon doped defect-rich catalysts in hydrogen production via dehydrogenation of hydrazine hydrate (HH). The synthesis of a new defect-rich catalyst capable of providing high hydrogen evolution rate in either catalytic or photocatalytic dehydrogenation of HH was aimed. For this purpose, “polymerization-induced colloid aggregation” (PICA) was proposed for the synthesis of carbon and nitrogen doped-mesoporous, gravel-like TiO2 microparticles (m-CN/TiO2 MPs) with a reduced band-gap energy of 2.3 eV. The Ti(III) content and oxygen vacancy concentration of pristine m-CN/TiO2 MPs were 6.06 % and 22.57 %, respectively. A defect-rich catalyst with high Ti(III) content (40.25 %) and high oxygen vacancy concentration (39.14 %) was obtained by the decoration of m-CN/TiO2 MPs with nickel-platinum nanoparticles (Ni-Pt NPs) via NaBH4 reduction (Ni-Pt/m-CN/TiO2 MPs) for the first time. The charge unbalance stimulated by Ti(III) species supported the formation of oxygen vacancies on m-CN/TiO2 MPs. The unique approach based on the synthesis of a C, N doped-mesoporous TiO2 based support by PICA and the deposition of Ni-Pt NPs by NaBH4 reduction in the presence of m-CN/TiO2 MPs allowed to obtain a heterogeneous catalyst with a low band energy of 1.7 eV for hydrogen production. The turnover frequency (TOF) values up to 1140.7 h−1 were achieved with 100 % H2 selectivity using the catalyst containing an active metallic site composed of 78.3 % mol Ni and 21.7 % mol Pt on m-CN/TiO2 MPs in the catalytic dehydrogenations performed at 323 K. The TOF values up to 530 h−1 with 100 % H2 selectivity were obtained by using Ni-Pt/m-CN/TiO2 MPs as a photocatalyst in the visible light driven photocatalytic dehydrogenation of HH at room temperature.